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Atomic layer deposited (ALD) tantalum nitride (TaxNy) is evaluated as a barrier against aluminum inside gate metal stacks of metal-oxide-semiconductor field effect transistor (MOSFET) devices. When deposited on hygroscopic oxides, like HfO2, amorphous tantalum nitride (a-TaxNy) is obtained, while deposition on Si or TiN results in polycrystalline Ta3N5. The low conductivity of both phases is not attractive for gate metal applications; however, a-TaxNy is crystallized to bixbyite Ta2N3 at 500 °C, improving its conductivity to ∼130 Ω−1 cm−1. For thicknesses below 10 nm, crystallization did not happen, but thin a-TaxNy barriers still obtain conductivity improvements to ∼500 Ω−1 cm−1 when Al diffuses into the film. In metal gate stacks, a-TaxNy screens the low work function of ALD TiAl more effectively than TiN. A barrier thickness reduction of 50% is achieved for n-MOSFET devices with an effective work function at 4.2–4.3 eV and low gate leakage. Slower diffusion of Al into TaxNy is observed by secondary ion mass spectroscopy; however, the cause of EWF lowering as a result of Al diffusion could not be confirmed. Instead, restoration of high EWF after removal of TiAl occurs, enabling an NMOS-first process integration with the use of 1 nm thin TaxNy barriers. [ABSTRACT FROM AUTHOR]

Mapping and visualization of all degradation modes in both n- and p-channel field effect transistors, specifically devices for dynamic random access memory periphery, is performed in the (VG, VD) bias space applicable for complementary metal-oxide-semiconductor operation. This "all-in-one" approach allows for tracking and studying in parallel all degradation regimes, including bias temperature instability, hot carrier degradation, and off-state stress, as well as the transitions between them. It should prove beneficial when developing new very large-scale integrated technologies, since it allows for simultaneous comparison and checking of all degradation regimes and promptly identifying "weak spots" of each technology option. It also allows to choose the correct criteria (voltages or fields) at a later time and postprocessing the data as necessary. [ABSTRACT FROM AUTHOR]

The scaling behavior of Gd- and Al-doped HfO2 films as gate dielectrics in metal-oxide-semiconductor (MOS) capacitors was studied. For equivalent oxide thicknesses (EOTs) in the range of 10Å, crystallized Gd:HfO2 showed higher leakage current densities than crystallized Al:HfO2, with undoped HfO2 in between. Ultimately, the scalability of Al:HfO2 was limited by the ability to crystallize the films at a given thermal budget. As a result, for post-deposition annealing at 800 C, the EOT of Al:HfO2 based MOS capacitors was limited to ~8Å . However, for such an EOT, leakage current densities were reduced by about 100× with respect to HfO2. This demonstrates the high potential of Al:HfO2 for low-standby-power MOS devices. [ABSTRACT FROM AUTHOR]

Examines electron transport properties through indium arsenide quantum dots in modulation doped structures. Drain current modulation with respect to gate voltage in the material; Measurement of valley current energy gaps and voltage difference between drain current peaks; Use of the quantum dot charging energy as an explanation basis of the gaps.